Johnson v. Towsley was a United States Supreme Court case that dealt with the issue of whether a state court had the authority to issue a writ of habeas corpus to a prisoner who was being held in a federal prison. The case arose when a prisoner, Johnson, was held in a federal prison in Michigan. Johnson sought a writ of habeas corpus from the state court, which the court granted. The federal government then appealed the decision to the Supreme Court. The Supreme Court held that the state court did not have the authority to issue a writ of habeas corpus to a prisoner held in a federal prison. The Court reasoned that the writ of habeas corpus was a federal prerogative, and that the state court did not have the authority to interfere with the federal government's power to imprison individuals. The Court also noted that the writ of habeas corpus was a fundamental right, and that the state court should not be allowed to interfere with the federal government's power to imprison individuals. In conclusion, the Supreme Court held that the state court did not have the authority to issue a writ of habeas corpus to a prisoner held in a federal prison. The Court reasoned that the writ of habeas corpus was a federal prerogative, and that the state court did not have the authority to interfere with the federal government's power to imprison individuals. The Court also noted that the writ of habeas corpus was a fundamental right, and that the state court should not be allowed to interfere with the federal government's power to imprison individuals.

In Johnson v. Towsley, the Supreme Court was asked to decide whether a contract between two parties could be enforced even though it had been made in violation of a state statute. The majority opinion held that the contract should not be enforced because it violated public policy and was therefore voidable at the option of either party. Justice Field dissented from this decision, arguing that contracts are generally enforceable unless they violate some positive law or interfere with an established public policy. He argued that since there was no positive law prohibiting such contracts nor any established public policy against them, then they should be upheld as valid and binding on both parties regardless of their illegality under state statutes. Furthermore, he asserted that if courts were allowed to invalidate contracts based solely on their illegality under state laws without considering other factors such as public policy considerations then it would lead to uncertainty and confusion in commercial transactions which would ultimately harm society more than upholding illegal agreements ever could.